The present invention relates generally to the field of automotive air-conditioning systems and, more particularly, to automotive air-conditioning refrigerant systems.
For illustration, FIG. 1 is a refrigerant flow diagram showing the major components of a conventional automotive air-conditioning refrigerant system 100 having a compressor 104, a condenser 105, an orifice tube 106 (or other similar limited flow pressure reducer), and an evaporator 108. Refrigerant 102 flows through the air-conditioning refrigerant system 100 in directions shown by refrigerant flow direction arrows 101. The air-conditioning refrigerant system 100 is subdivided into a system high-pressure side 110 and a low pressure side 112 as shown.
As illustrated in FIG. 2, a common mode of initial internal failure of current automotive air-conditioning refrigerant systems 100 is the catastrophic failure of an Original Equipment Manufacturer (“OEM”) component that was installed at the time of manufacture of the vehicle. In particular, OEM compressors 104 are susceptible to catastrophic failure of those component compressor parts internal to the flow boundaries of the air-conditioning refrigerant system 100. These component parts, such as compressor impellers, may fracture and introduce bits of solid debris 116 of various sizes into the air-conditioning refrigerant system 100. Regardless of the reason for the initial compressor 104 failure, catastrophic or non-catastrophic, it is probable that some debris 116 will be introduced into the air-conditioning refrigerant system 100 either during the failure itself or during the subsequent replacement of the compressor 104.
One of the major problems frequently encountered by mechanics engaged in the repair of an automotive air conditioning refrigerant system is the removal of such debris 116 from the air-conditioning refrigerant system 100. Repair or replacement of the OEM compressor 104, even with an OEM approved replacement, without the removal of substantially all the debris 116 created by the failure may cause reduced performance of the repaired air-conditioning refrigerant system 100 or even post-repair damage or failure of the replacement compressor 104. Various post-repair problems that may be caused by debris 116 include:
(1) reduced refrigerant flow resulting in excessively high pressures;
(2) an increase in refrigerant temperature caused by excessively high pressures;
(3) reduced compressor lubrication due to reduced refrigerant flow;
(4) excessive heating of compressor due to reduced refrigerant flow;
(5) excessive heating of compressor due to reduced lubrication; and
(6) physical damage to compressor components
Regardless of the reason for the initial compressor internal failure, some debris 116 will accumulate in the air-conditioning refrigerant system 100. Referring to FIG. 1, the direction of flow 101 of the refrigerant during normal operations is shown. Starting at the compressor 104, refrigerant 102 flows from the compressor discharge, through the condenser 105, and into the inlet of the orifice tube 106. This portion of the air-conditioning refrigerant system 100 is designated the high pressure side 110. Refrigerant pressure at the compressor discharge is typically between about 80 p.s.i.g. and about 200 p.s.i.g. and drops little until the refrigerant 102 flows through the orifice in the orifice tube 106. From the orifice tube outlet, refrigerant 102 flows through the evaporator 108 and into the compressor suction. Refrigerant pressure at the orifice tube outlet is typically around 45 p.s.i.g. and drops to 30 p.s.i.g. as the refrigerant 102 flows into the compressor suction. This portion of the air-conditioning refrigerant system 100 is designated the low pressure side 112. The air-conditioning refrigerant system 100 may have other components, such as an accumulator and/or drier that are not shown.
Referring now to FIGS. 1 and 2, as a compressor 104 begins to fail and emit debris 116, normal refrigerant flow 101 will introduce debris 116 into the high pressure side 110 and in particular, into the compressor discharge line. Immediately following major internal compressor failure, it is likely that the pressure differential between the high pressure side 10 and the low pressure side 112 will result in reverse flow through the compressor 104. Thus, it is likely that some of the debris 116 will be introduced into the low pressure side 112, and in particular, into the compressor suction line. A major internal compressor failure can cause some of the debris 116 to be carried by the refrigerant 102 throughout the refrigerant system and into all major air-conditioning refrigerant system components.
Compressors 104 are designed to pass debris 116 up to a certain size without damage to the compressor 104. Debris 116 above this size can damage the compressor 104 and sometimes cause complete failure of the compressor 104. As mentioned above, debris 116 can sometimes be found in all parts of the air-conditioning refrigerant system 100 after a component failure. Because of this possibility, a suction filter (not shown) should be installed at the compressor suction. Suction filters are usually designed with a filter mesh of 40 to 60, which will trap debris 116 of about 300 microns or larger. Some of the debris 116 which is small enough to pass through the compressor 104 may accumulate in the orifice tube 106 and cause reduced refrigerant flow.
The nature of the debris 116 released by a component failure depends on various factors, including: the particular system design, the composition of the failed parts, the type of failure encountered and the temperatures generated during failure. For instance, in the air-conditioning refrigerant system 100 of some makes of vehicles, debris 116 dissolved in the high temperature refrigerant fluid 102 discharged from the compressor 104 can accumulate as a solid or as sludge in the condenser 105 where the refrigerant 102 is rapidly cooled. In removing such debris 116, it is often necessary to apply heat to the condenser 104 before the debris 116 can be flushed from the system 100. There are numerous modes of failure and manner and location of debris 116 contamination.
Currently, there are several different conventional methods used to remove debris from the various air-conditioning refrigerant systems following component failure and replacement. One method is to blow out the air-conditioning refrigerant system with compressed air. Manufacturers do not recommend this method because of a possible hazard created when 134a refrigerant is combined with air under pressure. Also, the compressed air method is not a very effective method for removing debris from an air-conditioning refrigerant system.
Another method is to flow a flushing solvent under pressure through the air-conditioning refrigerant system to flush out the debris. This method requires the use of specialized flushing equipment that can currently cost from one hundred to several thousand dollars. Besides the expense of specialized equipment, the method requires a single use flushing solvent and specialized disposal methods for the contaminated flushing solvent. The flushing solvent and its disposal represent significant expense and environmental hazard. Although conventional flushing will remove most of the debris from an air-conditioning refrigerant system, it will not remove the debris which has solidified in the condenser. Also conventional flushing will not remove debris that is trapped between the refrigerant system hose connections and the refrigerant system hose material, or debris that has become embedded in the refrigerant system hose material. Moreover, incomplete removal of the flushing solvent can dilute the refrigerant oil. Dilution of the refrigerant oil can result in inadequate lubrication of the replacement compressor. This may cause premature failure of the replacement compressor.
Some mechanics simply replace all or almost all of the air-conditioning refrigerant system components that could contain debris. This method has the disadvantage of being expensive and labor intensive. Also, unless all of the components are replaced, the possibility still exists that some debris could remain in the air-conditioning refrigerant system and cause post repair failure or reduced performance.
A fourth method is to install an inline filter between the condenser and the orifice tube after installing a replacement compressor or other replacement component. This method will normally prevent debris from accumulating in the orifice tube. However, if significant amounts of debris were present following repair and then became trapped in the inline filter, the filtered debris may clog the filter. A clogged inline filter would block or partially block the flow of refrigerant. Such a reduction in refrigerant flow could cause the post repair problems mentioned above. Also, this method does not remove any debris that could be in the low pressure side of the air-conditioning refrigerant system.
A similar method is to install an inline filter in the low pressure side of the system, usually as near as possible to the compressor suction. One of the larger Original Equipment Manufacturers recommends this as part of all air-conditioning refrigerant system repair procedures whenever a compressor has been replaced. Although this would prevent any damaging debris from entering the compressor, this method does not remove any debris that could be in the high pressure side of the air-conditioning refrigerant system. Thus, this method should be combined with some other procedure designed to prevent debris from reducing the refrigerant flow in the high pressure side of the air-conditioning refrigerant system.
An alternative method is a flushing procedure commonly termed a ‘live flush’ and is frequently used to flush solid debris from the condenser. A ‘live flush’ normally requires the installation of a disposable filter in the liquid portion of the high pressure side of the air-conditioning refrigerant system, between the condenser and the orifice tube. After the repairs have been completed, the air-conditioning refrigerant system is operated for some period of time to allow the refrigerant to reach operating temperature. At operating temperature, the refrigerant dissolves the solid debris in the condenser and the debris is then trapped by the inline filter. After some period of time, usually about 1 hour, the air-conditioning refrigerant system is shut down. Next, the refrigerant and then the disposable inline filter are removed. Finally, the air-conditioning refrigerant system is recharged with refrigerant. Although this method removes any debris from the high pressure side, the compressor is not protected from potential damage caused by debris in the low pressure side. The additional labor time represent significant expense. Additionally, the replacement and disposal of the flushing refrigerant, and the use and disposal of the inline filter represent additional environmental impact and disposal costs.
Unfortunately, the Original Equipment Manufacturers are not in agreement as to which procedure or combination of procedures to recommend for the removal of debris. Until recently, one of the major Original Equipment Manufacturer did not recommend flushing as a way to remove debris from the system. They instead recommended the installation of a filter in the high pressure side of the air-conditioning refrigerant system, preferably between the condenser and the orifice tube. Original Equipment Manufacturer now recommends flushing after the repair of any major air-conditioning refrigerant system failure, but only with 134a refrigerant. While that Original Equipment Manufacturer continues to recommend installation of a filter in the high pressure side of the air-conditioning refrigerant system between the condenser and the orifice tube, they also recommend installation of an additional filter in the low pressure side of the air-conditioning refrigerant system 100 near the compressor suction.
While most Original Equipment Manufacturers and compressor re-builders recommend flushing an automotive air-conditioning system as a way to remove debris from the system, there is no agreement as to the optimal procedure. Examination of the various methods for flushing an automotive air-conditioning refrigerant system reveals several key steps that most of the Original Equipment Manufacturers and compressor re-builders would agree upon:
(1) loose and lightly adhered debris should be removed from the refrigerant system;
(2) the air-conditioning refrigerant system should be flushed with 134a refrigerant in place of or following a solvent flush to eliminate some of the problems associated with incomplete removal of flushing liquid;
(3) heat the flushing agent to increase the possibility of removing more of the debris from the air-conditioning refrigerant system;
(4) install an inline filter in the high pressure side to trap debris not removed by flushing;
(5) ensure that the orifice tube (or expansion valve) remains as clean as possible;
(6) replace the accumulator/drier or the receiver/drier (depending on the system); and
(7) install a suction filter in the low pressure side of the air-conditioning refrigerant system to trap debris.
Due to the high cost of automotive air-conditioning repairs and due to potential environmental impact of discarded filters, refrigerant and flushing solvent, it is desirable to remove the debris from the system in a cost effective manner with as little discard of filters, refrigerant and flushing solvent as possible. Each of the methods enumerated above has one or more disadvantage including: limited effectiveness in debris removal and preventing post repair component failure; excessive cost of materials; excessive labor time and labor cost; excessive cost of disposal; and excessive environmental impact upon disposal.
What is needed is a new method and apparatus to remove the debris from the air-conditioning refrigerant system in a time saving, cost effective manner with as little discard of filters, refrigerant and flushing solvent as possible.